A typical electrical connector comprises a plug member and a receptable member with a set of pin contacts on one member and a set of socket contacts on the other member. A coupling nut is rotatably mounted on one of the members and adapted for threaded engagement with the other member whereby the plug and receptacle members may be drawn together in an axial motion and without relative rotation, by rotation of the coupling nut.
In the use of such connectors, there has been a problem of making certain that the coupling nut has been advanced sufficiently so that the plug and receptacle shells are fully mated, i.e., the contacts are properly engaged; also in some connectors, metal-to-metal contact of the shells is important for electrical shielding and for stability of the mated conditions during vibration. Although the user may tighten the coupling nut until it feels like it has reached a stop or has "bottomed out", this may be misleading if the coupling nut is jammed or a foreign object interferes. Also, the use of soft elastomeric sealing gaskets makes it difficult to feel when the mating plug and receptacle shells have bottomed out. There is a need for means to provide a positive and unambiguous indication to the user that the coupling nut has advanced to a predetermined position and that the plug and receptacle are fully mated.
In the prior art, it is a common practice to provide a sight line on one of the connector members in such as position that it will be covered by a coupling nut when the full mate condition is reached. This allows a visual check for the full mate condition but it is ineffective when the connector is in a dark location or unaccessible to the view of the user. A connector with a detent means which also serves as an indicator is disclosed in U.S. Pat. No. 4,059,324.
A general object of this invention is to provide an improved means for indicating when a plug and receptacle are fully mated.